The present invention relates to a folding apparatus. More particularly this invention concerns a folding cylinder used in conjunction with a web-fed rotary press.
A rotary press normally prints several pages next to each other on a continuous web which is then subdivided into sheets each having on each side several, typically four, different pages. These sheets are folded, bound, and then trimmed to make a book or magazine.
In a standard rotary folding apparatus there is normally provided a rotatable folding cylinder having on its periphery a plurality of grippers each in a respective axially extending gripper slot. The centers of the sheets are tucked into these slots and the respective grippers are closed. The thus held sheets are then displaced by rotation of the drum to a release point.
It is normally possible to release the sheets at any of a plurality of angularly offset locations. As the grippers are normally operated by respective cam followers that ride on the periphery of a cam fixed relative to the cylinder, it is therefore necessary to change the contour of this cam in order to change the release location. German published specification 2,103,946 shows how this can be done by replacing the cams themselves. Thus to change release points it is necessary to at least partially disassemble the apparatus, entailing a relatively long downtime and a corresponding loss in plant efficiency. It has also been suggested to merely make the cam up of parts that allow its various lobes to be moved angularly about, however this solution also has proven rather cumbersome in use.
It has also been suggested in German Pat. No. 676,745 to use a pair of cams each with the respective cam follower for opening and closing the grippers. Each gripper, therefore, has two respective cam followers and is provided with a clutch that can connect it to either of these followers, depending on the release position. Such an arrangement has, however, shown itself very impractical in practice, and still does not allow for any degree of adjustment of the release position once the respective cam is selected. Furthermore use in a system having more that two release locations is impossible.